Case Presentation

We present a 7-year-old male with no previous medical history who developed progressive proximal muscle weakness and elevated ESR over three years with no response to prednisone, IVIG, or methotrexate. Before the muscle biopsy, he was presumed to have juvenile dermatomyositis, given concurrent pink discoloration over his metacarpophalangeal joints and proximal muscle weakness. The eventual biopsy demonstrated increased SDH and ragged-red fibers, and genetic sequencing confirmed the patient's m.3251 variant of the MT-TL1 gene. These findings established a highly unusual diagnosis of myopathy-predominant MELAS in a patient lacking seizure or stroke-like episodes, with an unremarkable brain MRI and possessing an uncommon genetic variant.

Discussion

We compare our case to other reports of primary presentation of MELAS in the literature. Though rare for a patient to have the m.3251 variant of the MT-TL1 gene with only two prior reports of this variant cited, it is perhaps even more unique that this patient suffered principally proximal muscle weakness as his presenting symptom, associated only with elevated LDH, CK and liver transaminases while lacking seizures, or stroke symptoms that would be expected. This case demonstrates the utility of reexamining muscle weakness in pediatric patients who are unresponsive to steroids in a presumed myositis-like picture. Through this elusive case of MELAS, we highlight the relevance and application of muscle biopsy, electromyography, and genetic testing to accurately diagnose and treat muscular weakness.